The present invention relates to a CO2 sensor for measuring the presence of the respiration and the CO2 partial pressure in the expiration, and also to a CO2 measuring apparatus including the CO2 sensor.
As a CO2 sensor for measuring the CO2 partial pressure in the expiration, there are a sensor based on the infrared spectroscopy method which uses infrared absorption of CO2 (see Patent Reference 1), that based on the dye method in which a pH change of an electrolytic solution caused by CO2 is detected as a color change of a pigment (see Patent References 2 and 3), and the like.
The sensor of the infrared spectroscopy method disclosed in Patent Reference 1 can measure the partial pressure without intubation, but is expensive, and has limitations in miniaturization and low power consumption. The sensors of the dye method disclosed in Patent References 2 and 3 are economical and have advantages that miniaturization and low power consumption are enabled. However, the sensors are of a type in which it is used while being disposed in a pipe connected to an intubation tube. Therefore, the sensors cannot measure the partial pressure without intubation, and hence their application range is limited.
(Patent Reference 1) JP-A-2003-315264
(Patent Reference 2) JP-A-06-249850
(Patent Reference 3) JP-A-63-75541